This invention relates to a piston assembly adapted for use in brakes or clutches. A conventional brake of the axially engaging type comprises a member rotatably mounted in a housing and a plurality of interleaved friction discs alternately mounted for limited axial movement on the member and on the housing and adapted to be compressed together to brake the member relative to the housing. The brake is normally held in its "on" condition of operation by a plurality of coil springs which urge an annular pressure plate against the friction discs to compress them together. An actuating chamber is defined in the brake whereby pressurization thereof will reciprocate a piston to disengage the pressure plate from the friction discs to permit the member to rotate relative to the housing.
In many such brakes, care must be taken to depressurize the actuating chamber prior to disassembly of the brake. Conventional brakes normally comprise a cap screw which normally closes a bleed orifice for relieving the air pressure in the actuating chamber upon removal of the cap screw. A typical bleeding arrangement is disclosed in U.S. Pat. No. 3,526,302, assigned to the assignee of this application.